Example 1: Heap sort in c++
using namespace std;
void heapify(int arr[], int n, int i)
{
int largest = i;
int l = 2 * i + 1;
int r = 2 * i + 2;
if (l < n && arr[l] > arr[largest])
largest = l;
if (r < n && arr[r] > arr[largest])
largest = r;
if (largest != i) {
swap(arr[i], arr[largest]);
heapify(arr, n, largest);
}
}
void heapSort(int arr[], int n)
{
for (int i = n / 2 - 1; i >= 0; i--)
heapify(arr, n, i);
for (int i = n - 1; i > 0; i--) {
swap(arr[0], arr[i]);
heapify(arr, i, 0);
}
}
void printArray(int arr[], int n)
{
for (int i = 0; i < n; ++i)
cout << arr[i] << " ";
cout << "\n";
}
int main()
{
int arr[] = { 12, 11, 13, 5, 6, 7 };
int n = sizeof(arr) / sizeof(arr[0]);
heapSort(arr, n);
cout << "Sorted array is \n";
printArray(arr, n);
}
Example 2: python code for heap using heapify
class heap:
def maxheapify(self,array):
n=len(array)
for i in range(n//2-1,-1,-1):
self._maxheapify(array,n,i)
def _maxheapify(self,array,n,i):
l=2*i+1
r=2*i+2
if l<n and array[l]>array[i]:
largest=l
else:
largest=i
if r<n and array[r]>array[largest]:
largest=r
if (largest!=i):
array[largest],array[i]=array[i],array[largest]
self._maxheapify(array,n,largest)
def minheapify(self,array):
n = len(array)
for i in range(n//2-1,-1,-1):
self._minheapify(array,n,i)
def _minheapify(self,array,n,i):
l=2*i+1
r=2*i+2
if l<n and array[l]<array[i]:
smallest = l
else:
smallest = i
if r < n and array[r]<array[smallest]:
smallest = r
if (smallest != i):
array[smallest], array[i] = array[i], array[smallest]
self._minheapify(array, n, smallest)
def descending_heapsort(self,array):
n = len(array)
for i in range(n // 2 - 1, -1, -1):
self._minheapify(array, n, i)
for i in range(n - 1, 0, -1):
array[0], array[i] = array[i], array[0]
self._minheapify(array, i, 0)
def ascending_heapsort(self,array):
n=len(array)
for i in range(n//2-1,-1,-1):
self._maxheapify(array,n,i)
for i in range(n-1,0,-1):
array[0],array[i]=array[i],array[0]
self._maxheapify(array,i,0)
b=[550,4520,3,2340,12]
a=heap()
a.maxheapify(b)
print('Max Heapify -->',b)
a.minheapify(b)
print('Min Heapify -->',b)
a.ascending_heapsort(b)
print('Ascending Heap Sort -->',b)
a.descending_heapsort(b)
print('Descending Heap Sort -->',b)
Example 3: heap sort
// @see https://www.youtube.com/watch?v=H5kAcmGOn4Q
function heapify(list, size, index) {
let largest = index;
let left = index * 2 + 1;
let right = left + 1;
if (left < size && list[left] > list[largest]) {
largest = left;
}
if (right < size && list[right] > list[largest]) {
largest = right;
}
if (largest !== index) {
[list[index], list[largest]] = [list[largest], list[index]];
heapify(list, size, largest);
}
return list;
}
function heapsort(list) {
const size = list.length;
let index = ~~(size / 2 - 1);
let last = size - 1;
while (index >= 0) {
heapify(list, size, --index);
}
while (last >= 0) {
[list[0], list[last]] = [list[last], list[0]];
heapify(list, --last, 0);
}
return list;
}
heapsort([4, 7, 2, 6, 4, 1, 8, 3]);
Example 4: heap sort heapify and max heap in binary tree
Implementation of heap sort in C:
int main()
{
int heap[10], array_size, i, j, c, root, temporary;
printf("\n Enter size of array to be sorted :");
scanf("%d", &array_size);
printf("\n Enter the elements of array : ");
for (i = 0; i < array_size; i++)
scanf("%d", &heap[i]);
for (i = 1; i < array_size; i++)
{
c = i;
do
{
root = (c - 1) / 2;
if (heap[root] < heap[c]) /* to create MAX heap array */
{ // if child is greater than parent swap them
temporary = heap[root]; // as structure is of complete binary tree
heap[root] = heap[c]; // it took logn steps to reach from root to leaf
heap[c] = temporary;
}
c = root;
} while (c != 0);
}
printf("Heap array : ");
for (i = 0; i < array_size; i++)
printf("%d\t ", heap[i]); //printing the heap array
for (j = array_size - 1; j >= 0; j--)
{
temporary = heap[0];
heap[0] = heap[j] ; /* swap max element with rightmost leaf element */
heap[j] = temporary;
root = 0;
do
{
c = 2 * root + 1; /* left node of root element */
if ((heap[c] < heap[c + 1]) && c < j-1)
c++;
if (heap[root]<heap[c] && c<j) /* again rearrange to max heap array */
{
temporary = heap[root];
heap[root] = heap[c];
heap[c] = temporary;
}
root = c;
} while (c < j);
}
printf("\n The sorted array is : ");
for (i = 0; i < array_size; i++)
printf("\t %d", heap[i]);
}